"ISIS just claimed the Degenerate Animal (sic) who killed, and so badly wounded, the wonderful people on the West Side, was 'their soldier'," Trump said in a tweet.

"Based on that, the military has hit ISIS 'much harder' over the last two days. They will pay a big price for every attack on us!" Trump said before he boarded Air Force One for his maiden trip to Asia.

Trump reiterated his tough message against ISIS just before he boarded Air Force One, on his way to Hawaii – the first stop of his Asia trip.

"What we're doing is every time we are attacked from this point forward and it took place yesterday, we are hitting them 10 times harder," Trump said.

"So when we have an animal do an attack like he did the other day on the West Side of Manhattan, we are hitting them 10 times harder," he said.

"They claim him as a 'soldier', good luck. Every time they hit us, we know it is ISIS, we hit them like you won't believe," he said.